1. Field of Art
The present invention relates generally to an apparatus and a method for optimizing the operation of an agricultural baler, and more particularly to sensing the capacity at which the baler is operating. In particular the baler is adapted to determine the ratio between an optimum rate of production of packages of crop material formed in the baling chamber of the baler and the actual flow rate of material entering the baler from the field. The present invention also includes a control system and method for determining the capacity at which the baler is operating, for example for determining the ratio between an optimum rate of production of packages of crop material formed in the baling chamber of the baler and the flow rate of material entering the baler from the field. The invention has particular application to optimizing the normal operation of the baler under conditions when charges of crop material fed into the baler are varying, such as on fields where there is a non-uniform crop yield.
2. Description of Prior Art
Conventional agricultural balers comprise a frame pulled behind a tractor over the field and picking up therefrom hay, straw or silage grass and feeding such crop material to a baling chamber in which it is compressed to packages. In one type of known baler the packages are parallelepiped is shape and are formed under action of a plunger which reciprocates inside the baling chamber. When the packages have reached a predetermined length a tying mechanism is operated to encircle the completed package with a plurality of strands and to knot the strands ends together to form a finished bale which is then ejected out of the baler. A baler with display in the driver cabin with associated microprocessor for a monitoring and control system for the baler is described, for example, in U.S. Pat. No. 4,624,180.
Commonly the baling chamber comprises a reciprocating plunger which is thrust against the package when a new charge of crop material is introduced into the chamber. To feed crop material into the chamber a crop pick-up assembly is provided with closely spaced tines located at ground level which feed the crop from the field into a duct. Optionally, the crop fed into the duct may be cut to a suitable size, for example, by feeding the crop through a set of knives. Ideally, the crop should be pre-compressed in the duct into uniform amounts of crop before it is transferred to the baling chamber. This may be achieved by packer forks which partly compress the crop against a restraint placed at the end of the duct Oust before the baling chamber). A stuffer mechanism transfers the pre-compressed crop into the baling chamber when adequate material is available in the duct. There are several ways that the correct transfer time can be determined, e.g. one known way is by means of a sensor which indicates when a pre-determined pressure has been achieved in the duct. Ideally, the packer operates continuously while the stuffer mechanism only operates when adequate material is present. In this way, unnecessary movement of the stuffer mechanism is avoided and equal amounts of crop are transferred to the baler chamber.
The drive for an agricultural baler is typically taken from a power take-off (PTO) at the rear of the tractor. Other than this energy source, other sources such as hydraulic power may be optionally provided from the tractor or generated on the baler from the PTO using a hydraulic pump. The PTO drive mechanism is used to drive all of the components of the baler. These components are activated at different times. Typically, the plunger will be operated at so many operations per minute, whereas the stuffing mechanism only operates when the crop in the duct has reached the correct pressure. To prevent the baler jamming it is necessary to co-ordinate the operation of the stuffing mechanism and the plunger. For instance, the stuffer mechanism should be inhibited if the plunger is not in a start position (thus, leaving the entrance to the baler chamber free). The stuffing mechanism is conventionally driven through a one-revolution clutch, i.e. once activated the drive clutch makes one revolution and then stops awaiting a further activation. The clutch drive for the stuffing mechanism operates when two criteria are fulfilled: when the crop density sensor has been activated and the plunger has returned to its start position. Depending on the rate of crop pick-up the ratio of plunger strokes to stuffer mechanism operations is an integer, e.g. 1, 2, 3. It is known to provide the driver of the tractor with an indication of this value. Examples of balers meeting the above description are the 4860 and 4880 big balers supplied by New Holland, N.V., Belgium.
One problem with the indication system described above is that it is limited to integer values. It would be advantageous to supply the driver with information of intermediate values if these are related to the actual amount of crop material being picked-up by the baler. This would allow the driver to adjust the speed of the tractor to optimize performance of the baler. In addition, no values below 1 are indicated to the driver. A value below 1 is an indication that more crop is being picked-up than can be baled under standard conditions, i.e. that sufficient crop material is ready in the duct (activation of first stuffer mechanism criterion) for the next stuffing operation before the plunger has returned to the start position (second stuffer mechanism criterion). This may not be a problem as some over-compression is tolerable. However, at some point the system is overloaded—usually resulting in the breaking of specially dimensioned shear bolts which are provided to prevent serious damage to the working components of the baler. However, replacing a shear bolt takes time and results in a lower efficiency.
As an alternative or addition to shear bolts, European Patent Application 876,752 describes the use of power-operated clutches. Monitoring of the operation of the baler is provided by sensors. If the revolution rate of a monitored operating element exceeds or falls below speed limits, the monitored operating element is switched off by activating the clutch. However, operating of the clutch stops operation of the relevant element so that efficiency must inevitably fall.
It is an object of the present invention, to provide an apparatus and method which allow the driver of a tractor pulling a baler to optimize the operation of the baler in a better way than is conventionally known.